Mikuni Fuel Pump. Is it really a fancy check valve?

WorkerB · Mar 28, 2009

I have a Troy-Bilt 7500 Watt generator (Generac) with a Briggs & Stratton engine. It has a Mikuni fuel pump model # 808492. The 5/16" port from the gas tank broke. JB Weld didn't work. New one is $34.00. It looks like the gas portion of the device is just a check valve. The third port goes to the crank case breather. Can I just put a check valve in line and leave the crankcase breather connected where it is? If I am correct anyone know of a source for a 5/16" check valve? Thanks in advance,
WorkerB

Willl · Mar 28, 2009

Can't tell by looking at your tiny pic, but if it has a port to the crank case then it's more than "a fancy check valve".

Most likely it uses the crank case pulses to power the diaphragm which in turn pumps your fuel.

Skyco · Mar 28, 2009

Exactly. Had the same principal at work on a 5HP Mierc outboard I had and on a 2006 Yamaha Rhino. Crankcase pressure pulses flex a diaphragm pumping fuel on the other side of said diaphragm. The check valve keeps it from going back to the tank.

Hooked_on_HP · Mar 28, 2009

The back pressure then vaccum in the crankcase makes the pump pump. It is not a check valve. Unless your gas tank is higher than your carb you need the pump.
Bill

KubotaSam · Mar 28, 2009

Hooked_on_HP said:
The back pressure then vaccum in the crankcase makes the pump pump. It is not a check valve. Unless your gas tank is higher than your carb you need the pump.
Bill

Even generators that have the fuel tank above the carb have this type of fuel pump. I am not sure but I think it keeps an even pressure of fuel into the float bowl of the carb to keep the RPM's constant. Without it when the tank was low on fuel there would not be as much gravity pressure to the carb and the engine might starve for fuel. I had trouble with mine during an ice storm this past winter. I think I paid $29.00 for mine.

Leejohn · Mar 28, 2009

It has 2 check valves, one in and one out.

WorkerB · Mar 28, 2009

OK, I get it. I called the local chain saw and small engine shop and the owner said he didn't have my exact brand and model number. He did however have a Honda brand fuel pump that would work. I also found a Makuni (Used) fuel pump that looked the same but I don't know the part number. How critical is it that I get the exact part number?